In my opinion, it is actually a lot better to read out loud. Tone of voice is super important for meaning, and you literally can't hear the tone as the author intended if you're reading things silently. So personally I think it's the other way around, I think reading silently is vastly inferior. People can swear up and down that they can read a million words a minute silently, but then they are just missing the point of reading, which is to hear the writer's voice.

The author is basically speaking to the reader. When you read a book out loud you are hearing the author.

Of course there's a time and a place for everything. Usually if I can't read something out loud, I will at least whisper the words quietly to myself. Furthermore, I think it's the silent readers who should practice reading out loud, which is a basic thing that every good reader should at least know how to do, even if they don't do it all the time. I think you should be comfortable doing both, but like I said, it's a more powerful experience reading out loud.